1 Gravity is a force that we experience every moment of every day. Gravity is the basic force in the universe. Every body (planet, moon, star, comet, asteroid, meteor, etc.) in the solar system has a force that pulls things to itself. That's gravity- the force of attraction between all objects in the universe.2 On Earth, it keeps people and objects from flying off into space. Gravity even keeps our air from floating off into space! An object's weight depends on the strength of the force of gravity. The pull of gravity is different on different bodies in space so weight varies on different planets or moons. For example, if you weigh 100 pounds on Earth, you would only weigh about 16 pounds on the moon. The moon is a smaller body than Earth and so its gravity is less.3 Isaac Newton discovered in the 1600s that the force of gravity depends upon the amount of matter (mass) in bodies and the distances between the bodies.